Wet combustion of waste liquors

ABSTRACT

Process are provided for the web combustion of waste liquors in which the waste liquor is reacted with oxygenating gas in a reaction vessel at a temperature between 450* F. and 705* F. at superatmospheric pressure, characterized in that superheated water condensed from the exit gaseous stream from the reaction vessel is added to the waste liquor prior to its entry to the reaction vessel.

United States Patent 1191 Morgan [4 Nov. 18, 1975 1 WET COMBUSTION OFWASTE LIQUORS 2932.613 4/1960 Huesler C181 210/63 3.2071572 9/1965 Saul162/31 X [75] lnvemor' John f Mwgan, 3,272739 9/1966 Earle et a1. 210/71x Australa 3.359.200 12/1967 011611616161. 210/63 73 A 1 34649l7 9/1969Porteous 210/71 X Sslgnee fffifitg g g gg fig 25:; x3 3.507788 4/1970C018 et al. 210/71 x 3,549,529 12/1970 Wiseman 210/63 [22] Filed: Apr.19, 1971 Primary E.\'aminerRobert Lindsay, Jr. [21] Appl' 1353 AssistantExaminer-William F. Smith v Attorney, Agent, or FirmPierce, Scheffler &Parker [30] Foreign Application Priority Data May 8 1970 Australia...;l1134/70 [57] ABSTRACT 1 Process are provided for the web combustion ofwaste [52] US. Cl. 162/31; 210/63; 210/71 liquors in which the wasteliquor is reacted with oxy- [51] Int. Cl. D2'1C 11/14 genating gas in areaction vessel at a temperature be- [58] Field of Search 162/30, 31;23/49; 210/63, tween 450 F. and 705 F. at Superatmospheric pres- 210/71sure, characterized in that superheated water con- 1 densed from theexit gaseous stream from the reaction [56] References Cited vessel isadded to the waste liquor prior to its entry to UNITED STATES PATENTSthe reaction vessel- 2,7's2,243 6/1956 Barton et a1. 162/31 3 Claims, 2Drawin Figures CONDENSATE 1 F1 1 H2. 1 T1 SPENT BLACK UQWR 1311.111:BLACK u Fl HI, Tl, F5. F3 HLTQI Fs QUOR WATER CUNDENSATE BLACK LIOUDR USPatent Nov. 18, 1975 CONDENSATE z 1 SPENT BLACK UQUOR D\LUTE BLACK UQUORWATER CONDENSATE BLACK LIQUOR WET COMBUSTION OF WASTE LIQUORS Thisinvention relates to improvements in the wet combustion of waste liquorscontaining combustible organic materials, and refers especially toimprovements which facilitate the wet combustion of black liquorobtained from the soda process for the pulping of wood, but theinvention can be employed with advantage for other waste liquors whichin terms of their nature, composition and concentration give rise tooperational problems generally similar in nature to those overcome bythe application of this invention to the wet combustion of soda processblack liquor.

An object of the invention, hereinafter described, is to avoid thenecessity to employ the known types of apparatus for indirect heatexchange in the wet combustion process, such apparatus being normallyessential for preheating of the waste liquor and air mixture requiredfor the process, and by avoiding the use of such apparatus, eliminatinginefficiencies caused by fouling or scaling of heat exchange surfacescaused primarily by the nature of adventitious impurities present intypical waste liquors and also waste material itself. Applicantsinvention in addition to achieving this object also achieves severalconcomitant advantages hereinafter described and these are reducedconsumption of water, reduction in power required for pumping andimproved precision of temperature control.

in the known method of applying the wet combustion process, the wasteliquor which contained combustible organic material in aqueous solutionor fine dispersion and also may contain in addition inorganic substancesin solution, is mixed with an oxygenating gas such as air undersuperatmospheric pressure. In this specification and in the claims theterm air is taken to include oxygen, oxygen-enriched air and otheroxygenating gases, since it is only the element oxygen which isrequisite for the operation of the process.

The aim of the process is to cause a reaction to occur between the saidoxygen and the organic materials of the waste liquor whereby the latterare substantially or completely destroyed, being converted finally tocarbon dioxide gas and water by oxidation-type reactions substantiallyidentical to those of normal combustion.

To achieve the aforesaid reaction it is required that the mixture ofwaste liquor and air be preheated to a predeterminedtemperature,'hereinafter referred to as the preheat temperature, atwhich temperature the reaction will proceed at a technically significantrate and become self-sustaining as a result of the exothermic heatproduced by the oxidation reactions.

When the reaction has been initiated by preheating the reactant mixtureto the desired vpreheat temperature, the mixture is transferred to asuitable pressure vessel, hereinafter referred to as a reactor, wherethe reactions are permitted to continue to the desired degree ofcompletion. For the purposes of the description which follows, theprocess is regarded as being one in which the reactant mixture is passedcontinuously through the system from inlet to outlet, but suchdescription does not exclude operation in a batch or semicontinuous modefor which the applicants invention may also be used with advantage.

The temperature of the mixture of waste liquor and air within thereactor is normally substantially greater than the temperature of thepreheated mixture since once the reaction is initiated the exothermicheat liber- 2 ated from such reaction raises the temperatureproportionately and thereby further increases the rate of reaction inaccord with known laws of chemical reaction.

In typical cases a desirable preheat temperature would be in the range230 to 350F and a desirable reaction temperature within the reactorwould be in the range 550 to 650F althougn these typical ranges are notexclusive of other temperature ranges in particular circumstancesprovided that no temperature at any point within the system exceeds thecritical temperature of water, namely 705.4F. I

The use of high reaction temperatures of the order of 600F is requisiteto ensure high degrees of oxidation in given reaction time determined bythe permitted time of residence of the mixture within the reactor andgoverned in practice by the need to employ a reactor having technicallyfeasible dimensions in relation to the desired throughput.

The establishment, maintenance and accurate control of the temperaturewithin the reactor is of utmost importance to the operation of thesystem. It is known that this temperature, when thermal equilibrium hasbeen established, depends on the preheat temperature and on the quantityof organics (i.e., organic substances) in relation to the quantity ofwater or water vapour within the reactor. The exothermic heat ofreaction is transferred quantitatively, excepting for adventitiouslosses of heat by radiation and conduction, to the aqueous phase whichin turn is partly converted to water vapour, the proportion of watervapour to water in the liquid phase being dependent on the temperatureand pressure extant in the system and calculable from knownthermodynamic relationships. If the quantity of water in relation toorganics is excessive the reactor temperature cannot rise to the desiredvalue as the exothermic heat available will be insufficient in relationto the quantity of water. At the other extreme a high concentration oforganics and relatively small quantity of water may result in thesituation that substantially all water is vapourised as the temperaturerises close to the critical temperatures of water. In practice theconcentration of organics in the aqueous phase has to be initiallyadjusted such that the desired reaction temperature is attained whilemaintaining sufficient water in the reactor at all times to keep theorganic substances in true solution or fine dispersion and in particularto keep desired or adventitious inorganic residues in true solution. I

When, for a given waste liquor, a desirable initial concentration hasbeen thus established to achieve a satisfactory reaction temperature andthereby a desired degree of oxidation and reaction rate, the wasteliquor, together with the requisite quantity of air, has to be preheatedto the calculated preheat temperature for the purposes of initiating thereaction. The sum total of the heat added as preheat plus the heatevolved by the exothermic reaction thus controls the maximum reactortemperature attained within the reactor subject only to adventitiousheat losses.

In the pre-existing art the water liquor may be concentrated by knownmeans, such as evaporation, or alternatively diluted with water fromexternal sources to obtain the desired initial concentration. The wasteliquor suitably adjusted in concentration is then mixed undersuperatmospheric pressure with the requisite quantity of air and theadmixture passed through a suitable indirect heating apparatus such as ashell and tube heat exchanger to obtain the desired preheat temperatureprior to entering the reactor. Alternatively the water. waste liquor andair may be separately heated by indirect heat exchange and then mixed inthe required proportions. The heat required for preheating may besupplied from external sources or recuperated from the exit liquid orgaseous streams leaving the reactor since these are at a suitably hightemperature to exchange their heat to the incoming mixture.

Applicant has found that the known methods of indirect preheating of theincoming mixture of air and waste liquor or alternatively the wasteliquor by itself have serious practical and economic disadvantagesbecause the heat exchange surfaces foul or scale readily due to factorsinherent in the nature of many waste liquors and in particular caused byadventitious inorganic impurities frequently present in such liquors.Such fouling or scaling of the heat exchange surfaces limits theefficient transfer of heat after short periods of operation andapplicant has found it may eventually result in a complete blockage ofthe waste liquor side of the heat exchanger. Applicant has found furtherthat the scales causing the fouling may be very difficult to remove byphysical or chemical means and may cause the process in terms of theknown art to be inoperable in practice for many waste liquors. In thecase of soda process black liquor applicant has found that the scalesare variable in chemical composition but consist essentially of calcium.magnesium, sodium, alumina and silica together with carbonate anionsderived from impurities in the waste soda process liquor. Such scalesderived from soda process waste liquor greatly limit the efficiency ofthe prior art of wet combustion for use with such liquors and therebylimit the utilisation of the process for these and similar liquors.

The fact that this nature of scale has been established for soda processwaste liquor should not, for the purposes of the invention hereinafterdescribed, be taken to exclude scales of other natures derived eitherfrom organic or inorganic constituents of waste liquors in general andwhich may be similarly disadvantageous. Further, applicant has alsoestablished that scales may form from substances in natural waters usedto dilute waste liquor whether or not scale forming substances arepresent in the waste liquor before dilution. Such scales formed fromsubstances in natural waters are generally of the inorganic typedescribed above and may be compared with those known to form in steamboiler tubes when impure water is used. Applicant has also found thatwhere the indirect heat exchange is arranged to derive its heat sourcefrom the hot exit liquor after reaction (known hereinafter as oxidisedliquor) such liquor has severe fouling and scaling properties since theinorganic impurities orginally present in the waste liquor remainsubstantially unchanged but become more concentrated in the exitoxidised liquor from the reactor. As a result the fouling problem mayoccur on both sides of indirect heat exchangers giving rise to a furtherlimitation of the present art which it is desired to recuperate heatfrom that available after reaction and which procedure is otherwiseeconomically advantageous.

Applicant has discovered that the above disadvantages arising fromindirect heat exchange for preheating in association with the complexand variable nature of waste liquors and dilution water, may besubstantially avoided by a novel method whereby direct exchangepreheating and the requisite dilution of waste liquor may be achievedsimultaneously by utilising su- 4 perheated pure water obtained fromwithin the reaction system itself.

In the novel method of the applicant the waste liquor is preferably notprediluted with water from external sources but if required may bepreconcentrated by conventional means. Applicants invention avoids theuse of indirect heat exchangers for the purposes of preheating theadmixture of waste liquor and air by providing a condensing surface inthe exit gaseous stream from the reactor and other ancillary devices.The exit gaseous stream from the reactor normally consists substantiallyof carbon dioxide, water vapour and also nitrogen in the case where theoxygenating gas used is air. The water vapour is derived from the waterin the reactor and in quantity is substantially that which is requiredto saturate the non-condensible gases in the exit stream at theequilibrium temperature and pressure of the reactor. The water vapour togas weight ratio in the exit gaseous stream depends on the compositionand nature of non-condensible gases and on the equilibrium temperatureand pressure in the gaseous phase.

When such water-saturated gaseous stream is allowed to impinge on acooler-surface water vapour condenses as a consequence of the reducedtemperature and such water may be then separated from the gaseous streamby known means such as suitable traps or separation apparatus.

By suitable adjustment of the temperature at which condensation ispermitted to occur and with the system pressure being maintainedsubstantially constant the proportion of water vapour condensed can becontrolled and furthermore the temperature of such condensed water canbe arranged to be substantially higher than the desired preheattemperature but necessarily lower than the maximum reaction temperature.

In the method of the applicants invention a suitable condensing surfaceindirectly cooled by external water, external air or other externalcooling fluid is arranged in the exit gaseous stream from the reactor.Condensation is permitted to occur such that the temperature of thecondensed water phase is substantially greater than the desired preheattemperature. The condensed water is collected by suitable separationapparatus and transferred and if necessary raised in pressure by meansof a suitable pump or other device in order that the requisiteproportion of this condensed water may be directly injected into andadmixed with the inlet stream of waste liquor and air prior to admissionof the mixture into the reactor. In this way applicant's inventionprovides both the necessary preheat and simultaneously providesnecessary dilution to the waste liquor/air mixture thus avoiding anynecessity for indirect heat exchange and overcoming the limitations ofthe prior art as previously described.

Applicant's method has several evident concomitant advantages. Thecondensed water obtained as above for dilution is substantially free ofdissolved solids and unlike natural waters cannot contribute furtheradventitious impurities to the waste liquor stream as may occur with theuse of natural waters for dilution. This is of advantage in minimizingscaling tendencies later in the system since the quantity ofscale-forming impurities in the oxidised liquor is maintained at theminimum level and cannot exceed the quantity orginally introduced by thewaste liquor itself before dilution.

Another advantage is the reduction in power required to pump liquor intothe system which necessarily operates at superatmospheric pressuresfrequently of the order of 200 atmospheres. If for the purposes ofdescription it be assumed that the initial concentrated waste liquormust be diluted at some stage with water in the ratio of one part ofwaste liquor to one part of water, which is typical of the case of sodaprocess black liquor, then it is evident that if pre-dilution is notemployed, as in the applicants method, the volume of'liquor to be raisedto the superatmospheric system pressure is reduced by half therebyapproximately halving the power used in pumping. In the applicantsinvention the dilution water obtained by condensation is approximatelyat the system pressure and is retained at such pressure by a suitableinterim or buffer storage device. In order to pass it into the stream ofwaste liquor and air the suitable pump has only to overcome the smallpressure difference between the inlet and outlet points of the reactor,such pressure difference being only the sum of the hydrostatic head ofthe reactor plus pipeline and reactor friction losses, and such pressuredifference arising from these causes may be typically from one to eightatmospheres.

It is also obvious that many factors in the operation of the applicantsmethod are controlled by highly predictable and calculable thermodynamicrelationships and that the transfer of heat at all points is direct andhighly quantitative and unlimited by external influences. Therefore, byits nature applicants invention offers more precise control oftemperature and dilution in the preheating stage than previouslypossible. Applicants method is therefore highly amenable to automatic'control.

The invention will be further described in the following, taken with theaccompanying drawing, in which FIG. 1 is a simplified flow sheet of theprocess of the invention, and

FIG. 2 is a diagrammatic representation of a system of apparatusadaptable for use in carrying out the process of the invention.

In the applicant's invention the following equations may be used todescribe the balances of heat and materials on a general theoreticalbasis and without consideration of minor corrections arising fromadventitious losses of heat by radiation or conduction or from minorendothermic chemical reactions which may proceed within the systemalongside the predominant characteristic exothermic oxidation reactions.

The basic parameters of the system are expressed by the followingalgebraic symbols and when substituted by numeric values must be in aconsistent system of units. For clarity of expression the units areshown below in the British system but any consistent system may be used.

When,

F flow rate of combustible (oxidisable) organic solids in waste liquorexpressed as pounds per hour and,

F, flow rate ofwater in the initial undiluted waste liquor expressed aspounds per hour and,

F flow rate of water derived from waste liquor as condensate within theprocess expressed as pounds per hour and.

F flow rate of water in waste liquor after dilution with condensaterepresented by F and expressed as pounds per hour and.

T, temperature of undiluted waste liquor expressed in degrees Fahrenheitand.

T temperature of condensate water derived within the process from wasteliquor and expressed in degrees Fahrenheit and,

T temperature of waste liquor after dilution with condensate derivedfrom within the process and expressed in degrees Fahrenheit and,

c specific heat of solids in waste liquor expressed as British ThermalUnits per pound per degree Fahrenheit and,

H enthalpy of water present in the initial undiluted waste liquor at thetemperature (T of such liquor and expressed in British Thermal Units perpound and,

H enthalpy of condensate water at temperature T derived within theprocess from waste liquor and expressed in British Thermal Units perpound and,

H enthalpy of water at temperature T in waste liquor after dilution withcondensate derived within the process and expressed in British ThermalUnits per pouhd then, with reference to FIG. 1 of the accompanyingdrawings, the following equations apply.

( l s) 2 11 x) and therefore,

F2=F;,-F| (1) Above equation 1 defines the water balance and can be usedto determine the required flow rate of condensate.

Also,

FIHI s 'u l F2: zi zi s 'n a and therefore,

z z a u I I a 'u (TFTI) and substituting for F by equation (1) then,

(fir EH 2 a .1 I I s 'p zf il whereby,

Above equation (3) can be used to determine condensate temperature whenF H T F and 0,, are predetermined by waste liquor feed conditions and FH and T are predetermined by maximum desired or allowable reactiontemperature and maximum desired or allowable concentration of solids insolution in the reactor at the maximum or any reaction temperature.

A practical example of the embodiment of the applicants invention in areaction system for the wet combustion of waste liquor derived from thesoda process of pulping wood is now described with reference to FIG. 2of the accompanying drawings. Waste liquor from the soda process ofpulping, hereinafter called black liquor, was processed in a suitablewet combustion system the equipment components of which were arranged inaccord with the flow sheet shown in FIG. 2 and this arrangementpermitted the wet combustion process to be operated on a continuous flowbasis.

The composition of the initial black liquor before processing andignoring minor constituents and expressed on the basis of actualquantity of black liquor constituents per hour of operation was 156,561pounds of water (per hour) 34.569 pounds of total dissolved solids (perhour) and such 34.569 pounds of solids included 10,897 pounds of sodiumin combined form but calculated and expressed as the equivalent weightof sodium hydroxide. The initial supply temperature of the black liquorto the process was 181F.

The said black liquor was pressurized to just greater than 3,050 poundsper square inch gauge pressure by means of Pump 1 and thereby introducedinto the reaction system which was maintained by suitable devices at acontrolled average gauge pressure of 3,000 pounds per square inch. Thesystem pressure ranged from 3,050 pounds per square inch at thedischarge of Pump 1 to 2,850 pounds per square inch at the high pressureside of the system outlet valves that is: 8, 13, 14. This pressuredifference from system inlet to outlet was due to factors such as pipefriction and hydrostatic head in the Reactor 5.

At T-junction 2 air at the rate of 151,915 pounds per hour on the drybasis was injected into the black li' quor such air being compressed toa suitable desired pressure of 3,050 pounds per square inch gauge andalso being at a temperature of 460F. The high temperature of such airwas acquired as a result of partial adiabatic air compression but suchtemperature of the air is incidental and not relevant to the applicantsinvention except that it must be known to compute the thermal balance inconjunction with other given conditions.

At T-junction 3 situated close to T-junction 2, and prior to the inletpoint 4 of Reactor 5 water condensate obtained from within the processby arrangements hereinafter described was injected into the mixture ofblack liquor and air at the rate of 108,150 pounds of water per hour andthe temperature of this water condensate was 460F. The injection of thiscondensate into the black liquor-air mixture was achieved by means ofPump 12 which was a suitable device to raise the pressure of thecondensate from 2,900 pounds per square inch to 3,050 pounds per squareinch. This pressure difference substantially represents small pressurelosses through the system attributable to pipe friction and relatedfactors previously mentioned.

As a result of the heat derived by direct contact heat exchange from thepreheated air (which was proportionately very small) and in particularthe large amount of heat derived by direct contact heat exchange fromthe water condensate added at T-junction 3 the temperature of the totaladmixture was raised to 310F. Simultaneously the proportion of watercondensate introduced at T-junction 3 reduced the concentration of totalsolids in the liquid phase of the mixture from 2.05 pounds per gallon ofliquor existing at the inlet of Pump 1 to 1.254 pounds per gallon ofliquid phase after T- junction 3 and prior to the inlet point 4 ofReactor 5.

The desired temperature of 310F was thus achieved in the mixture of air,water condensate and black liquor and the desired concentration of totalsolids at 1.254 pounds per gallon of liquid phase simultaneouslyachieved these conditions having been found to be requisite in the caseof soda process black liquor to maintain a satisfactory rate of reactionand to maintain all solids in solution when the Reactor 5 was operatedat a maximum temperature of 608F.

At the top of Reactor 5 a suitable Separator 7 was incorporated wherebythe steam and non-condensible gas phases were separated continuouslyfrom the liquid phase. At the top of Reactor 5 where the temperature wassubstantially 608F the proportion of steam to noncondensible gas wassubstantially greater than the proportion of steam to non-condensiblegas existing at the lower temperature of 310F at the entrance point 4 ofReactor 5 or at any temperature intermediate between 310F and 608F, suchintermediate temperatures representing the rise in temperature occuringas a result of 8 exothermic reactions during the passage of the reactantmixture from the entrance 4 to the exit 9 of Reactor 5. The steam thusgenerated within the reactor was substantially free of dissolved solidsand demonstrated to form substantially pure water after condensation.

The liquid phase or oxidisable liquor collected at the base of Separator7 was discharged continuously via a suitable liquid discharge Valve 8suitably controlled to maintain constant level in Separator 7.

The steam and non-condensible gas phase obtained at the top of Separator7 consisted of 180,165 pounds of steam (per hour) 152,682 pounds (perhour) of noncondensible gas consisting substantially of nitrogen, carbondioxide and a small proportion of oxygen, together with 7,634 pounds(per hour) of entrained water, such water being the result of bothphysically incomplete separation and a small reduction in temperature ofthe steam/gaseous phase caused by unavoidable thermal losses. At pointof discharge 9 of the steam/- gaseous phase from the Reactor 5 thetemperature was 606F.

The mixture of steam and non-condensible gas from Reactor 5 was passedthrough the tubes of a suitable shell and tube Heat Exchanger 10 wherebyits temperature was reduced to 470F thereby condensing 162,683 pounds(per hour) of steam to produce the same weight of water condensate at atemperature of 470F. The condensation was effected by indirect heatexchange to water at about 460F or less which was passed at a suitablerate through the shell side of Heat Exchanger 10.

The partially condensed mixture of non-condensible gas, steam and waterwas then passed to a further Separator 11 in which substantially all thewater condensate was separated from the balance of the steam and gaseousphase. The water condensate so separated was withdrawn continuously fromthe base of Separator 11 at a rate of 108,150 pounds of water per hourat a temperature of 470F and at a pressure of 2,900 pounds per squareinch gauge. By means of Pump 12 this water condensate was elevated inpressure from 2,900 pounds per square inch gauge to 3,050 pounds persquare inch gauge and injected at T-junction 3 into the mixture of airand initial black liquor. The temperature of the water condensateimmediately prior to the point of injection was 460F the reduction intemperature of 10F in the temperature of the water condensate being dueto adventitious heat loss. The balance of 54,533 pounds (per hour) ofwater condensate not utilised was passed to waste via outlet valve 14but it will be obvious to those skilled in the art that more or lesscondensate can be used in the manner described to vary the preheattemperature and concentration of the mixture prior to admission toReactor 5 and in a precise manner and which is desirable for thepurposes of process control.

In this manner and by the use of the applicant's invention as describedthe required preheat temperature of 310F and the required concentrationof 1.254 pounds per gallon of total solids in the liquid phase wasachieved at the point of entrance of Reactor 5 without the use of otherdevices such as indirect heat exchangers subject to fouling or scalingfor example with soda process black liquor.

1 claim:

1. A continuous process for the wet combustion of a waste liquorcontaining combustible constituents in which the waste liquor is reactedwith oxygenating gas in a reaction space at a temperature between 450 F.

9 and 705 F. at superatmospheric pressure, which comprises a.establishing a stream of waste liquor and heated oxygenating gas;

b. passing said stream into and through a reaction space to produce anexit stream consisting of steam, non-condensible gas and liquid phasewherein the proportion of steam to non-condensible gas in the exitgaseous stream from the reaction space is substantially greater than inthe waste liquor inlet stream at the inlet to the reaction space, thesteam thus generated within the reaction space being substantially freeof dissolved solids;

c. passing said exit stream, from the reaction space,

through a separator to separate the steam and noncondensible gas fromthe liquor phase;

d. passing the steam and non-condensible gas from the separator througha condenser in which superheated water is condensed at asuperatmospheric pressure slightly less than the pressure existing atthe inlet of said reaction space;

e. raising the pressure of this superheated water to at least thepressure in the reaction space; and

f. injecting the superheated water under pressure into the stream ofwaste liquor and heated oxygenating gas at step (a) prior to the entryof said stream into the reaction space,

the temperature of the injected pressurized superheated water beinghigher than the temperature of the undiluted waste liquor in said streambut lower than the maximum reaction temperature in the reaction spaceand being sufficient to raise the temperature of the stream ofoxygenating gas and diluted waste liquor to not less than 230 F. andsimultaneously to dilute the waste liquor to a predetermined extent.

2. A process according to claim 1, wherein the temperature of theinjected pressurized superheated water is between 450 F. and 650 F.

3. A process according to claim 1 wherein the exit gaseous stream fromthe reaction space is passed through a separator to separate the steamand non-condensible gas from the liquid phase, the steam andnoncondensible gas are passed through a heat exchanger where water iscondensed, the partially condensed mixture of non-condensible gas, steamand water condensate is passed to a second separator where the watercondensate is separated from the balance of the steam and gaseous phase,and the water condensate is raised in pressure and injected intothewaste liquor and oxyg'enating gas stream prior to its entry to thereaction space.

1. A CONTINUOUS PROCESS FOR THE WET COMBUSTION OF A WASTE LIQUORCONTAINING COMBUSTIBLE CONSTITUENTS IN WHICH THE WASTE LIQUOR IS REACTEDWITH OXYGENATING GAS IN A REACTION SPACE AT A TEMPERATURE BETWEEN 450*F.AND 705*F AT SUPERATMOSPHERIC PRESSURE, WHICH COMPRISES A. ESTABLISHINGA STREAM OF WASTE LIQUOR AND HEATED OXYGENATING GAS; B. PASSING SAIDSTREAM INTO SAID THROUGH A REACTION SPACE TO PRODUCE AN EXIT STREAMCONSISTING OF STEAM, NON-CONDENSIBLE GAS AND LIQUID PHASE WHEREIN THEPROPORTION OF STEAM TO NON-CONDENSIBLE GAS IN THE EXIT GASEOUS STREAMFROM THE REACTION SPACE IS SUBSTANTIALLY GREATER THAN IN THE WASTELIQUOR INLET STREAM AT THE INLET TO THE REACTION SPACE, THE STEAM THUSGENERATED WITHIN THE REACTION SPACE BEING SUBSTANTIALLY FREE OFDISSOLVED SOLIDS; C. PASSING SAID EXIT STREAM, FROM THE REACTION SPACE,THROUGH A SEPARATOR TO SEPARATE THE STEAM AND NON-CONDENSIBLE GAS FROMTHE LIQUOR PHASE; D. PASSING THE STEAM AND NON-CONDENSIBLE GAS FROM THESEPARATOR THROUGH A CONDENSER IN WHICH SUPERHEATED WATER IS CONDENSED ATA SUPERATMOSPHERIC PRESSURE SLIGHTLY LESS THAN THE PRESSURE EXISTING ATTHE INLET OF SAID REACTION SPACE; E. RAISING THE PRESSURE OF THISSUPERHEATED WATER TO AT LEAST THE PRESSURE IN THE REACTION SPACE; AND F.INJECTING THE SUPERHEATED WATER UNDER PRESSURE INTO THE STREAM OF WASTELIQUOR AND HEATED OXYGENATING GAS AT STEP (A) PRIOR TO THE ENTRY OF SAIDSTREAM INTO THE REACTION SPACE, THE TEMPERATURE OF THE INJECTEDPRESSURIZED SUPERHEATED WATER BEING HIGHER THEN THE TEMPERATURE OF THEUNDILUTED WASTE LIQUOR IN SAID STREAM BUT LOWER THAN THE MAXIMUMREACTION TEMPERATURE IN THE REACTION SPACE AND BEING SUFFICIENT TO RAISETHE TEMPERATURE OF THE STREAM OF OXYGENATING GAS AND DILUTED WASTELIQUOR TO NOT LESS THAN 230* F. AND SIMULTANEOUSLY TO DILUTE THE WASTELIQUOR TO A PREDETERMINED EXTENT.
 2. A process according to claim 1,wherein the temperature of the injected pressurized superheated water isbetween 450* F. and 650* F.
 3. A process according to claim 1 whereinthe exit gaseous stream from the reaction space is passed through aseparator to separate the steam and non-condensible gas from the liquidphase, the steam and non-condensible gas are passed through a heatexchanger where water is condensed, the partially condensed mixture ofnon-condensible gas, steam and water condensate is passed to a secondseparator where the water condensate is separated from the balance ofthe steam and gaseous phase, and the water condensate is raised inpressure and injected into the waste liquor and oxygenating gas streamprior to its entry to the reaction space.